1. Field of the Invention
The present invention generally relates to a self-adjusting apparatus for use in cleaning surfaces of endless belt conveyor belt apparatuses, and the like.
2. Description of the Prior Art
When bulk material such as coal, coke, sinter, stone, ore, and the like are transported on endless belt conveyor belts, oftentimes some of the materials do not drop off the discharge end of the conveyor belt. Such materials, which may be of a moist or putty-like consistency, stick to the conveyor belt, with a substantial portion of the materials shaking off the belt as the belt returns to the tail-end section of the conveyor apparatus. The materials so shaken off may build up on the floor below the conveyor belt apparatus, to such an extent that the materials may surround components of the apparatus, such as for example the return and training idlers of the conveyor belt, thereby detraining the belt and damaging the components of the conveyor apparatus. Such build-up of materials around the conveyor belt apparatus requires clean-up of the area, replacement of damaged return and training idlers, belts, end pulleys, snub pulleys, and other components of the conveyor belt.
Many different types of conveyor belt cleaning devices have been used in the past in an attempt to deal with the material carried back from the discharge end of the conveyor belt. For example, brushes have been positioned past the discharge end point and in contact with the conveyor belt to brush material from the belt. However, the material has the tendency to build up and compact and cake between the bristles of the brushes thereby rendering the brushing action ineffective.
Streams of compressed air have also been used to clean conveyor belts. However, the cost of generating such compressed air is quite high and the use of compressed air frequently creates turbulence which results in a dusty environment around the conveyor belt apparatus.
Likewise, single scrapers or scrapers with multiple hard blades have been used in an attempt to clean conveyor belts. Generally, these scrapers are mounted behind the head pulley; however, hard scrapers currently in use in the industry often damage or destroy the conveyor belt and do not clean properly the belt. Other scrapers utilized to clean conveyor belts include blades made from soft, flexible material, with the blades mounted on the head pulley. Such scrapers are quite inefficient and frequently result in damage to the conveyor belt when grit and other small particles lodge between the flexible scraper and the conveyor belt thereby causing a "sandpaper" effect when the conveyor belt is operated.
As is well known in the art, when the conveyor belt leaves the discharge end pulley, it begins to change shape from a straight-line cross section to a concave cross section having intermittent wave action. This occurs until the conveyor belt reaches the snub pulley or the first return idler, at which point the belt, because it is supported on the snub pulley or the first return idler, again achieves a straight-line cross section. Thus, when the conveyor belt is not supported, a cross section of the belt would take a concave shape having an intermittent wave action.
Even though it has been recognized that the unsupported conveyor belt takes a concaved shape, most conveyor belt cleaning devices in the prior art are installed behind the head pulley in the area where the belt is unsupported. These devices, which have either single or multiple scraping blades having a straight-line cross section, are rigidly mounted or, in some instances, mounted by springs. Because of the concave shape of the conveyor belt at such locations, frequently the scraping blades do not fully contact the conveyor belt across its width. Rather, the ends of such blades make contact with the belt, while the center portion of the blades do not. In such instances, material adhering to the conveyor belt is not cleaned off in the area near the center of the cleaning blades; this has a further disadvantage because as the material travels through the void between the conveyor belt and the center portion of the cleaning blade, the center portion is worn faster than the ends thereof. This causes the ends of the blades to become sharpened by wear and cut grooves into the face of the belt. It is for this reason that cleaning blades utilized in such cleaning apparatus are replaced very frequently.
In a further effort to avoid the conveyor belt damage noted above, some prior art devices have cleaning blades constructed in an arcuate shape. Such devices assume that the curved blade will match the shape of the conveyor belt as the belt passes thereacross. However, because these devices are installed at a location where the conveyor belt is unsupported, the belt may not assume the exact curvature of the blade. Thus, cleaning devices having such blades have the disadvantage similar to that discussed above with respect to straight blades; that is, the edges of the curved blades, because they do not touch the belt, are worn excessively by the material being carried back by the conveyor belt. This results in the center portion of the blades becoming sharp and destroying the belt as described above, while the material sticking to the conveyor in the area underlying the edges of the blade remains on the belt and is not removed.
The prior art has also recognized that the better location for a cleaning apparatus is on the head pulley. At this position, the flexible conveyor belt is still wrapped on the pulley and is supported by that pulley. This results in a belt which is flat and does not have the concaved or wavey attributes associated with an unsupported belt. In addition, at this location a flat cleaning blade could make flush contact with the surface of the belt. As a further advantage, the cleaning blade at this location is directly above the main discharge end chute such that the material scraped off the conveyor belt would fall with the bulk material being unloaded.
However, prior art cleaning devices which are positioned at the location where the conveyor belt is wrapped and supported by the head pulley are comprised of a single or double flexible bar, such as rubber or urethane, supported by a continuous steel bar. This apparatus is pressed against the surface of the conveyor belt and is pivotably supported by levers mounted parallel to the conveyor belt. The flexible bar cleaning apparatus is forced into the face of the conveyor belt by means of counterweights or springs. Such devices provide several disadvantages. First, the flexible conveyor belt itself often exhibits uneveniness due to uneven wear; that is, the center of the conveyor belt wears faster due to the fact that generally more material travels on the center of the belt than along the outer edges. Because of this, constant pressure of the cleaning bar cannot be achieved across the width of the conveyor belt so the cleaning efficiency is reduced. In addition, contaminants not detachable by the cleaning bar or a slight out of roundness of the head pulley will cause the cleaning bar to bounce from the surface of the belt thereby causing the cleaning bar to miss portions of the belt.
In order to counteract the above problems, prior art devices have increased the contact forces associated with the cleaning bar such that the cleaning bars are firmly held in contact with the conveyor belt. In order to do so, the cleaning bars must be made of a soft, flexible material because a hard material, such as, for example, steel or tungsten carbide, will damage the surface of the conveyor belt at increased contact pressures. It has been found, however, that when such soft, flexible materials are used as cleaning bars, small particles of the material removed from the surface of the conveyor belt will be imbedded in the face of such cleaning bars. This results in such cleaning bars acting with a sandpaper effect on the surface of the conveyor belt thereby damaging the belt.
The novel apparatus of the present invention overcomes the foregoing deficiencies noted in the prior art by providing an apparatus which cleans the surface of conveyor belts and removes therefrom material that is not discharged from the discharge end of the conveyor belt. The present invention accomplishes this result in a manner which minimizes damage to the surface of the conveyor belt. Accordingly, it is an object of the present invention to provide an apparatus for cleaning conveyor belts which does not have the inherent deficiencies of the prior art.
It is yet another object of the present invention to provide a cleaning apparatus which includes one or more blade tips positioned in contact with the surface of the conveyor belt at a location where the conveyor belt is in contact with the head, or other, pulleys of the conveyor belt system, thereby allowing material to be removed from the conveyor belt in an efficient manner.
It is yet a further object of the present invention to provide a cleaning apparatus which is self-adjusting in that the blade tips move in response to deformities of the head, or other, pulleys and the conveyor belt surface and in that the blade tips remain in contact with the belt surface as the tips wear during use.
These and other objects and avantages of the present invention will become apparent to those skilled in the art with reference to the foregoing, the attached drawings, and the description of the invention which hereinafter follows.